A ballistic pendulum consists of a wooden bob suspended from two cords. A bullet (or some other projectile) is fired into the wooden bob and the pendulum is used to measure the velocity of the projectile. The projectile's momentum is converted from the bullet to the bob and based off of the amplitude of the bob's swing, the velocity of the projectile can be calculated. The height and mass of the bob is needed for the calculations along with the velocity of the bob after the collision and the mass of the bullet.
This image shows the breakdown of the various components at work in a ballistics pendulum.
This is a simplified version of the ballistics pendulum.
This is an image of a pendulum kit that probably costs way too much.
A ballistic pendulum consists of a wooden bob suspended from two cords. A bullet (or some other projectile) is fired into the wooden bob and the pendulum is used to measure the velocity of the projectile. The projectile's momentum is converted from the bullet to the bob and based off of the amplitude of the bob's swing, the velocity of the projectile can be calculated. The height and mass of the bob is needed for the calculations along with the velocity of the bob after the collision and the mass of the bullet.
http://hyperphysics.phy-astr.gsu.edu/hbase/balpen.html
http://www.britannica.com/EBchecked/topic/50669/ballistic-pendulum
This image shows the breakdown of the various components at work in a ballistics pendulum.
This is a simplified version of the ballistics pendulum.
This is an image of a pendulum kit that probably costs way too much.